Collaborative Research: Investigating Photoinduced Charge Transfer Dynamics Across Molecule-Nanocrystal Interfaces

植物利用阳光将二氧化碳转化为富含能量的糖分子，这一过程被称为光合作用。人工光合作用系统的开发将产生巨大的社会效益，这种系统可以利用阳光从二氧化碳中生产酒精，从水中生产氢气。然而，化学反应是复杂的，涉及多个电子转移步骤，将这些步骤与光的吸收联系起来仍然是一个挑战。在化学系化学结构、动力学和机理A以及大分子、超分子和纳米化学项目的支持下，罗切斯特大学的David McCamant、霍鹏飞和Kathryn Knowles教授与布法罗大学、纽约州立大学的Luis Velarde教授和David Watson教授以及D‘Youville学院的Kacie Liwosz教授合作，研究染料分子和半导体纳米颗粒之间的光诱导电子转移反应。他们和学生一起种植由二氧化钛和氧化铁等常见矿物组成的纳米颗粒，并在它们表面涂上有机染料。然后，他们将精密的激光光谱仪与计算机建模相结合，以表征染料分子吸收光时发生的电子转移过程。除了培训下一代科学家外，该团队还在向上发展的暑期学校为有弱势背景的高中生举办教育研讨会。暑期工作坊激发了学生对可再生能源和化学的好奇心和热情，并鼓励他们在STEM领域继续接受高等教育。光致界面电荷转移是将太阳能转化为化学能的基本过程，在光催化燃料形成反应中尤为重要。详细了解半导体表面分子物种的基态、光激发态和电荷分离态的构象和电子结构，对于从机理上理解此类电荷转移反应的动力学是至关重要的。该项目结合了时间分辨电子和振动光谱学、和频产生光谱学、量子动力学模拟以及纳米结构半导体的制造和表征方面的跨学科专业知识。这些工具正被应用于与界面电荷转移有关的三个重要领域：(I)分子结构在调节界面电荷转移之前的弛豫和能量转移途径中的作用，(Ii)宽禁带p型半导体的形态与表面分子敏化剂的空穴注入之间的结构-功能关系，以及(Iii)窄带隙半导体的形态与向表面束缚的分子空穴和电子受体(如燃料生产催化剂)的电荷转移之间的结构-功能关系。通过这项工作产生的基本机械见解可以使半导体/分子伙伴系统的合理设计具有更好的从阳光光催化产生燃料的性能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Plants use sunlight to convert carbon dioxide into energy rich sugar molecules, in a process known as photosynthesis. The development of artificial photosynthetic systems that could use sunlight to make fuels such as alcohol from carbon dioxide and hydrogen from water would have enormous societal benefit. However, the chemical reactions are complicated and involve multiple electron transfer steps and connecting these steps with the absorption of light remains a challenge. With support from the Chemical Structure, Dynamics and Mechanisms A and Macromolecular, Supramolecular and Nanochemistry programs in the Division of Chemistry, Professors David McCamant, Pengfei Huo, and Kathryn Knowles at University of Rochester are teaming up with Professors Luis Velarde and David Watson at the University at Buffalo, State University of New York and Kacie Liwosz at D'Youville College to study light-induced electron transfer reactions between dye molecules and semiconductor nanoparticles. Working with their students, they grow nanoparticles composed of common minerals such as titanium dioxide and iron oxide and coat them with organic dyes. They then combine sophisticated laser spectroscopies with computer modeling to characterize the electron transfer process that occur when the dye molecules absorb light. In addition to training the next generation of scientists, the team is also running educational workshops in Upward Bound summer schools for high-school students with disadvantaged backgrounds. The summer workshops inspire students' curiosity and enthusiasm about renewable energy and chemistry, as well as encourage them to pursue higher education in STEM fields. Photoinduced interfacial charge transfer is a fundamental process underlying the conversion of solar energy to chemical energy and is particularly important in photocatalytic fuel-forming reactions. Detailed knowledge of the conformation and electronic structure of the ground, photoexcited, and charge separated states of molecular species bound to semiconductor surfaces is critical to a mechanistic understanding of the dynamics of such charge transfer reactions. The project combines interdisciplinary expertise in time-resolved electronic and vibrational spectroscopy, sum-frequency generation spectroscopy, quantum dynamics simulation, and the fabrication and characterization of nanostructured semiconductors. These tools are being applied to three important areas relating to interfacial charge transfer: (i) the role of molecular structure in mediating relaxation and energy transfer pathways that precede interfacial charge transfer, (ii) structure-function relationships between the morphology of wide band-gap p-type semiconductors and hole injection from surface-bound molecular sensitizers, and (iii) structure-function relationships between the morphology of narrow band gap semiconductors and charge transfer to surface-bound molecular hole and electron acceptors, such as catalysts for fuel production. Fundamental mechanistic insights generated by this work could enable the rational design of semiconductor/molecule partner systems with improved performance in photocatalytic generation of fuels from sunlight.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.